1. Field of the Invention
This invention relates to containers having a flexible cover sealable to a rigid base.
2. Prior Art
It is known to seal a flexible cover onto a rigid base by means of an inflatable tube. See for example U.S. Pat. Nos. 3,850,214; 4,028,853: 4,114,668; 4,117,575; 4,140,191 and 4,140,237.
Such containers commonly have an impermeable base and the cover is made impermeable. Air may be evacuated from within the cover so that the flexible cover is drawn down onto any goods on the base. This cover thus secures the goods on the base as well as forming a protection preventing the ingress of air or moisture. Such containers can be used therefore not only for the storage of goods but also for the transport of goods.
One convenient way of securing the cover on the base is to form the base with a slot or groove and to provide a flexible inflatable tube along the edge of the flexible cover, the tube being insertable into the slot or groove and inflated so as to be brought into pressure engagement with the walls of the slot or groove. A construction of this kind is described in the specification of U.S. Pat. No. 3,850,214. The inflatable tube may be attached to or integral with the cover or it may be a separate tube, for example housed within the slot or groove or attached to a side wall thereof and serving to seal against the peripheral edge of the cover.
In order to effect a good seal without excessive pressure in the tube, longitudinal ribs or projections may be formed along one side face of the slot or groove. When the tube is inflated, the ribs bite into the tube (or, if the tube is separate from the cover sheet, into the cover sheet between the upturned edge and the inflatable tube) in order to give localised pressure and hence a good seal.